Synthesis of brookite-type TiO₂ nanoparticles by emulsion-assisted hydrothermal method using titanium glycolate complex

We present a method for synthesizing brookite-type titanium dioxide (TiO₂) using an emulsion-assisted hydrothermal approach and a water-soluble titanium complex with glycolic acid as a complexing agent. In this study, stirred hydrothermal synthesis was used to synthesize water-in-oil emulsions with titanium glycolate complex in the aqueous phase. The resulting brookite-type TiO₂ was investigated using Raman spectroscopy for crystal polymorph identification, X-ray Diffraction to identify crystal polymorphs and crystallite size, Transmission Electron Microscope for primary particle size, and crystal shape, and Dynamic Light Scattering for TiO₂ secondary particle size in aqueous dispersion. The synthesized brookite-type TiO₂ was a needle-like crystal with a width between 20 and 30 nm and a length of more than 70 nm, growing in the b-axis direction at an angle of about 70° from the (120) plane. Furthermore, compared to the conventional synthesis method, the secondary particle size was smaller, and the dispersibility in water was improved. The results show that the brookite-type TiO₂ dispersion obtained using the emulsion-assisted hydrothermal method can facilitate the formation of uniform films and can be applied to the electron transport layer of organic perovskite solar cells.